// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
/*
 ******************************************************************************
 * Copyright (C) 1996-2016, International Business Machines Corporation and   *
 * others. All Rights Reserved.                                               *
 ******************************************************************************
 */

package com.ibm.icu.util;

/**
 * Interface for enabling iteration over sets of &lt;int index, int value&gt;, where index is the
 * sorted integer index in ascending order and value, its associated integer value.
 *
 * <p>The result for each iteration is the consecutive range of &lt;int index, int value&gt; with
 * the same value. Result is represented by &lt;start, limit, value&gt; where
 *
 * <ul>
 *   <li>start is the starting integer of the result range
 *   <li>limit is 1 after the maximum integer that follows start, such that all integers between
 *       start and (limit - 1), inclusive, have the same associated integer value.
 *   <li>value is the integer value that all integers from start to (limit - 1) share in common.
 * </ul>
 *
 * <p>Hence value(start) = value(start + 1) = .... = value(start + n) = .... = value(limit - 1).
 * However value(start -1) != value(start) and value(limit) != value(start).
 *
 * <p>Most implementations will be created by factory methods, such as the character type iterator
 * in UCharacter.getTypeIterator. See example below.
 *
 * <p>Example of use:<br>
 *
 * <pre>
 * RangeValueIterator iterator = UCharacter.getTypeIterator();
 * RangeValueIterator.Element result = new RangeValueIterator.Element();
 * while (iterator.next(result)) {
 *     System.out.println("Codepoint \\u" +
 *                        Integer.toHexString(result.start) +
 *                        " to codepoint \\u" +
 *                        Integer.toHexString(result.limit - 1) +
 *                        " has the character type " + result.value);
 * }
 * </pre>
 *
 * @author synwee
 * @stable ICU 2.6
 */
public interface RangeValueIterator {
    // public inner class ---------------------------------------------

    /**
     * Return result wrapper for com.ibm.icu.util.RangeValueIterator. Stores the start and limit of
     * the continuous result range and the common value all integers between [start, limit - 1] has.
     *
     * @stable ICU 2.6
     */
    public class Element {
        // public data member ---------------------------------------------

        /**
         * Starting integer of the continuous result range that has the same value
         *
         * @stable ICU 2.6
         */
        public int start;

        /**
         * (End + 1) integer of continuous result range that has the same value
         *
         * @stable ICU 2.6
         */
        public int limit;

        /**
         * Gets the common value of the continuous result range
         *
         * @stable ICU 2.6
         */
        public int value;

        // public constructor --------------------------------------------

        /**
         * Empty default constructor to make javadoc happy
         *
         * @stable ICU 2.4
         */
        public Element() {}
    }

    // public methods -------------------------------------------------

    /**
     * Returns the next maximal result range with a common value and returns true if we are not at
     * the end of the iteration, false otherwise.
     *
     * <p>If this returns a false, the contents of elements will not be updated.
     *
     * @param element for storing the result range and value
     * @return true if we are not at the end of the iteration, false otherwise.
     * @see Element
     * @stable ICU 2.6
     */
    public boolean next(Element element);

    /**
     * Resets the iterator to the beginning of the iteration.
     *
     * @stable ICU 2.6
     */
    public void reset();
}
